\begin{lstlisting}[frame=shadowbox, language=C, numbers=left, breaklines=true, basicstyle=\footnotesize]
#include "Controlar.h"

int is_regular (const char* filename) {
   struct stat sb;
   stat (filename,&sb);
   if (errno != 0 )
      fprintf (stderr, "ERROR: %s. %s\n",filename,strerror(errno));
   else if (S_ISREG (sb.st_mode) == 0)
      fprintf (stderr, "ERROR: %s is not a regular file\n",filename );
   errno = 0;
return S_ISREG (sb.st_mode);
}
\end{lstlisting}
